The current invention relates to an apparatus for cooling and/or heating a motor vehicle.
In modern vehicles, various units secondary to the engine are used, which are referred to below as units or secondary units. Such secondary units can be electric machines such as starters or generators, or also oil coolers and air conditioning compressors. In many cases, it is necessary to cool the secondary units in a manner similar to that of the engine.
On the other hand, the significantly increased efficiency of modern engines, for example direct injecting diesel engines, places ever increasing limits on the amount of heat generated by the internal combustion engine that remains available for other uses in the cooling and heating system of the vehicle. In some operating states of an engine, for example in the case of a cold start, when used for short trips, or even when the vehicle is traveling down long descents, the amount of heat input into the cooling water, which heat can be supplied by the engine itself, is no longer sufficient. As a result, the engine and its catalytic converter do not reach the optimal operating temperatures in the available amount of time, which leads to increased fuel consumption and exhaust emissions.
Since modern internal combustion engines, in particular the above-mentioned diesel engines, have become so efficient that they no longer generate enough thermal output to heat the vehicle interior or to de-ice the vehicle windows when temperatures outside are low, it is becoming more and more common to use secondary heaters, which are integrated into the cooling and heating circuit of the vehicle in order to impart additional heat to the cooling water in certain operating states of the engine.
Secondary heaters of this kind are either electrically operated or burn fuel (chemical secondary heaters) in order to generate the necessary heat. These secondary heaters are quite expensive and also have the disadvantage that they must be installed in the generally cramped engine compartment of a motor vehicle and therefore incur costs that are not insignificant.
For these reasons, it has been proposed to use heat sources that are already present in the vehicle system as additional secondary heaters for the cooling and heating system of the motor vehicle.
EP 08 41 735 A1 has disclosed a water-cooled alternating current generator or three-phase current-generator, which is used in motor vehicles and whose cooling jacket is integrated into the cooling water circuit of the internal combustion engine. The water flowing through the cooling jacket of this electric machine makes it possible to very effectively dissipate the impermissible dissipated energy of the generator. Moreover, there is the advantage that by contrast with air-cooled generators, this dissipated energy is not lost, but can be dissipated into the cooling water or a heating system by means of a heat exchanger and is consequently available for improving the thermal output.
DE 34 42 350 C2 has disclosed a heat exchanger system for heating a street vehicle with an electric drive motor. The power electronics, which are used to control the drive motor and which give off heat during driving operation, are provided with apparatuses for liquid cooling. The cooling connections of these apparatuses are connected by means of a closed conduit system to a pump and a heating system, which can dissipate heat into the interior of the vehicle. As a result, the heat dissipated by the power semiconductors via the heat sinks can be supplied to the heating system.
One main problem in imparting dissipated energy from electronic power semiconductors, for example also from starters or generators, into the cooling circuit of a vehicle lies in preventing the permissible component temperature of the semiconductor elements from being exceeded when cooling water temperatures are high.
DE 199 60 960 C1 has disclosed a heat exchanger system for a vehicle with an internal combustion engine and an electric motor, whose motor cooling circuit is equipped with a mechanical water pump and whose electronics cooling circuit is equipped with an electric water pump. The two cooling circuits are coupled to each other by means of connecting lines that can be opened and closed so that the heat, which is dissipated by the power electronics by means of the cooling water, can be used to heat the cooling water and therefore to heat the passenger compartment by means of the heating system heat exchanger.
The heat exchanger system disclosed in DE 199 60 960 C1 is very costly and complex so that in addition to the increased susceptibility of this system, its high costs must also be viewed as a non-negligible disadvantage.
A special edition of the Automobiltechnischen Zeitung (ATZ) [automotive engineering journal] and Motortechnischen Zeitung (MTZ) [engine design journal] from May 1998 disclosed a heating and cooling concept for a motor vehicle in which the water cooler of the system is serially divided into a high-temperature and low-temperature section. This division of the cooler enables two different flow speeds to be achieved. By installing a dividing wall in the water tank of the cooler, approximately 20% of the cooler wetting surface in the lower region of the cooler is used to produce a low-temperature section. A throttled coolant flow in the low-temperature region produces almost twice the temperature cooling rate as in the upper cooler region, which, due to its higher flow speed, only achieves a temperature reduction of approximately 7 degrees Celsius when used for cooling.